Alternating current relays

ABSTRACT

A solenoid construction for use as a power relay in which a phase-splitting magnetic core element in combination with a bistable snap-switch element enables a compact relay construction yielding a forward power control ratio of 4,800 : 1, or an equivalent power gain in excess of 36 decibels, without amplification.

United States Patent 1 91 Lang 1 1 May 22, 1973 [54] 3,249,823 5/1966Beardow ..335/258 5 2,458,957 l 1949 N 'lCl [76] Invent Greg" Lang 295Street, 3,553,618 151971 L31 ..335 244 Suffield, Conn. 06078 22 Filed;Jam 4, 7 Primary ExaminerI-larold Broome 211 App]. No.: 103,429

[57] ABSTRACT [52] US. Cl. ..335/244, 335/99, 335/297 51 Int. (:1 .1107/10 A use as a PM?r relay m 58 Field of Search "335/244 297 243 which aphase'splimng magnetic elemen 335/99 101 100 102 bination with abi-stable snap-switch element enables 6 6 a compact relay constructionyielding a forward power control ratio of 4,800 l, or an equivalentpower gain [56] References Cited in excess of 36'decibels, withoutamplification.

UNITED STATES PATENTS 6 Claims 3 Drawing Figures 1 3,281,741 10/1966Beliveau ..335/258 3,210,616 10/1965 Severn ..335/258 Patented May 22,1973 lll FIG.

I N VENTOR.

FBG.2

G REC-30R L. LANG ALTERNATING CURRENT RELAYS BACKGROUND This inventionrelates to improvements in alternating current electromagnets useful insolenoid devices such as valves, clutches, actuators, and particularlyin power relays used to. control substantial electrical loads. Whileuseful in compact light-duty general purpose relays, it is particularlyapplicable to power circuit relays whereby loads of hundreds orthousands of watts are controlled by actuating signals of relatively lowpower, and for convenience is herein shown and described as appliedthereto.

This application contains subject matter in common with my copendingapplication No. 783,035 for Phase Splitting Core for electro-magneticDevices, filed Dec. 11, 1968. (To issue Jan. 5, 1971, U.S. Pat. No.3,553,618.)

Power relays of the present type have evolved over many years within acommon body of prior art, and are available from many sources inrelatively standardized forms. Structures, mountings, terminals, contactarrangements, solenoid designs and other principal elements are similar.The functional parameters including contact current rating, responsetime, solenoid input wattage, temperature rise and service life arequite uniform for a given load rating. Switching contacts have beenfound to require substantial mechanical forces thus requiring actuatingsolenoids of relatively high power. It is common practice to providefrom 8.0 to 16.0 ounces of solenoid tractive force per switch pole, inrelays used in load circuits involving 20 to 30 amperes at 200 to 500volts.

Prior art solenoids for the present use almost invariably utilizelaminated magnetic cores, provided with copper shading rings to attainphase-splitting necessary to overcome the weak tractive forces andobjectionable buzz which is otherwise characteristic of single phaseelectromagnets. Shading-ring solenoids operate at low values ofefficiency therefor requiring relatively high values of input power, perunit of tractive force attained. It is well known that D.C. solenoidsyield as much as ounces of tractive force per watt of input, whereasA.C. shading-ring solenoids produce only 3.0 to 4.0 ounces per watt.Thus for a given force requirement a relatively high wattage must bedissipated by the solenoid, therefor requiring relatively large solenoidassemblies having large numbers of costly copper windings in the magnetcoil. High input wattage and the associated rapid and detrimentaltemperature rise have been commonly accepted as unavoidable incidencesof A.C. relay constructions heretofore available.

A further problem has evolved with the growing usage of power relays ascontrol elements in complex automated electro-mechanical systems forindustrial process control, automatic machine control, and likeapplications. Command signals for the power relays are commonly derivedfrom relatively sensitive or delicate sources such as electroniccomputers, or sensing devices responsive to thermal, speed, pressure,flow, or weight variables. Such sensors frequently yield signals oflimited power, inadequate to directly energize a power relay unlessadded amplification or an intermediate relay are employed. Suchaccessories add materially to system costs, and impair the overallsystem reliability.

Power relays for such applications are frequently viewed as controlamplifiers whereby a given load circuit maximum power is controlled by amuch lower input or solenoid wattage. The ratio of output power tocontrol or input power represents a forward gain or power-amplificationratio which numerically describes the merit of the device. As anexample, a commercial prior art A.C. relay of D.P.D.T. type has a switchrating of 25 amperes resistive load at 250 V. r.m.s, or 6,250 watts. Thesolenoid operates at 11.0 VA. or 7.0 watts, producing 21 ounces of forceat rated voltage. The control ratio is: 6,250/7 890 1, equivalent to29.5 decibels. Much higher power ratios are desirable and have long beensought in the prior art. In this regard it is noted that a relay ofsimilar load rating actuated by a D0. solenoid would operate at 2.5watts coil input, yielding a power ratio of 2,500 1, or 33.9 decibelspower gain, however usually requiring a DC. power supply.

Past efforts to overcome the above limitations have included carefulattention to design details of A.C. so-

lenoids, as well as resort to DC. solenoids supplied from auxiliarypower supplies, or energized by A.C. applied through full-wave diodebridge rectifiers. Preamplification is also sometimes applied, but issubject to similar cost, reliability, and power supply objections.Efforts to reduce solenoid wattage requirements by reducing relay springforces and contact pressures have generally resulted only in decreasedreliability and contact life expectancy, slower response time, andincreased susceptibility to malfunction due to mechanical shock loads orvibration.

The basic and long standing problem is clearly that of providing meansof constructing a relay actuator operated by A.C., which yields agreatly increased value of tractive force per watt of input, and whichis producible at costs comparable to prior art shading ring solenoids.

THE PRESENT INVENTION My copending application No. 783,035 referencedabove discloses a general purpose A.C. solenoid actuator incorporating anovel magnetic core element having inherent phase-splitting propertieswhereby the use of copper shading-rings is avoided. The simple and lowcost solenoid construction disclosed has been found to yield tractiveforce values in excess of 10 ounces per watt. 1 have discovered that amodification of the above structure enables its use in combination withvarious switch arrangements for relay constructions. The preferred formdisclosed herein embodies the modified solenoid in combination with acommercially available snap-switch element of high power handlingcapability. Power relays so constructed have been found to yield controlratios of greater than 4,500 l, or the equivalent power gain of 36.5decibels.

It is accordingly a principal object of the present invention to providein an A.C. actuated relay an actuating solenoid of greatly increasedmagnetic efficiency whereby current switching contacts are operable withsubstantially lower solenoid input wattage than has heretofore beenrequired.

Another object is to provide a new and improved A.C. relay constructionwhich utilizes a novel electromagnetic structure of linear acting typewhich combines high magnetic efficiency with low heat dissipation andtemperature rise, while yielding an increased value of actuating forcefor given dimensions.

A further object is to provide an improved A.C. relay of reduced sizefor a given load switching capacity wherein a novel magnetic actuator oflinear acting type enables construction at low cost with a minimum ofparts, and with wearing parts such as hinge pins, bearings and the likesubstantially avoided.

An additional object is to provide a novel relay construction ofrelatively high power-switching capacity in which the mass of movingparts is held to a minimum, thus enabling long mechanical life and rapidresponse to energizing signals of low power, yet which operates quietlyand with less impact noise than has commonly been attained by priorconstructions.

Still another object is to provide a relay of a low cost and compactconstruction having a high power switching capability, embodying a novelsolenoid actuator of improved efficiency, such that the volume andweight of copper winding required is substantially reduced over priorconstructions of similar power switching capacity.

A further object is to provide a novel relay construction of relativelyhigh efficiency and power switching capacity having external meanswhereby manual actuation of the switch means may be conveniently andsafely performed without exposure to shock or other hazard.

The foregoing and other objects and advantages of the invention willbecome apparent from the following description and the accompanyingdrawings describing various embodiments thereof.

In the drawings,

FIG. 1 is a side elevation of an assembled relay according to thepresent invention; and,

FIG. 2 is an enlarged partially sectioned view of the relay of FIG. 1showing a median section of a solenoid assembly in general accordancewith my above referenced copending application, as modified for thepresent relay usage; and,

FIG. 3 is an enlarged partially sectioned view of the phase-splittingcore assembly of FIG. 2.

Alternating current relay constructions heretofore available haveuniversally attained flux phase-splitting by the use of copper shadingrings placed in slots in the magnetic pole face abutting the theattracted member or armature, in a manner such as to encircle a majorportion of the pole-face area. The flux wave flowing in the encircledpole area is caused to lag in phase behind that of the wave flowing inthe unshaded pole area by the opposing and phase retarding effects ofthe heavy current circulating in the shading ring. A two-phase flux waveis thus generated. While such methods attain a moderately effectivesplit-phase result, the relatively low efficiency and highcharacteristic temperature rise enforce the requirement for relativelylarge and costly solenoid assemblies, for a given mechanical force.

Generally speaking the present invention makes use of my prior discoverythat flux phase splitting may be attained by the use in a solenoid coreportion, of two or more ferro-magnetic members in a parallel spacedarrangement, and having dissimilar electromagnetic properties includingmagnetic hysteresis and eddycurrent susceptibility. Those propertiescombined in one of said members cause the flux wave flowing therein tolag materially behind the wave flowing in the companion member which isdesigned to be relatively less susceptible to those retardantproperties. 'The above mentioned spacing between members enables themaintenance of interphase magnetic separation to avoid commingling orinter-phase coupling.

The foregoing art has enabled the attainment of very high values ofefficiency thus permitting compact solenoid constructions yielding highvalues of force per watt with low temperature rise. The above referencedcopending application contains a more detailed description of the art invarious applications, as well as a discussion of the properties ofvarious magnetic materials usable therein. Common reference charactersare used in FIGS. 2, and 3, of the drawings of both applicationswherever applicable.

The preferred exemplification of the present present invention makes useof a bi-stable plunger actuated snap-switch, long available from anumber of sources in relatively standardized forms and sizes. Such areavailable with contact ratings of from 5 to 25 amperes, having long beenaccepted as reliable and conservatively rated, and having found wide usedue to their compactness, low cost, and ease of replacement. Their usefor relay purposes has been inhibited presumably by the relatively highplunger force necessary to overcome the internal return spring.

The switch model chosen for initial development and shown herein is of aS.P.D.T. type, rated at 20 amperes A.C. resistive load at voltagesto'480 r.m.s. The linear actuating force required is 18.0 to 20.0ounces, a value clearly not attainable with prior art solenoids ofsuitably compact size and low input wattage. Conversely, the solenoidconstruction disclosed herein has a volume of 0.58 cubic inch, andyields a linear force of 21 ounces with power input of 2.0 watts, thusbeing ideally suited to the present combination.

The above circumstances have enabled the construction disclosed which isof the straight-through linear acting type, in which levers, bearings,hinge-pins and qther commonly used parts are avoided. Relays of the typedisclosed have exhibited exceptional life and reliabilitycharacteristics, test models having attained 1.5 X 10 operational cycleswithout failure. Switching response has been found to be exceptionallyrapid, presumably due to the relatively high value of solenoid forceavailable, combined with the relatively low mass or weight of the movingparts of the solenoid and switch, taken separately or together.

It will be apparent from the above recited ratings and performancevalues that the relay herein described attains a control ratio of9,000/2 4,500 l, or 36.5 decibels power gain, a result heretoforeunattainable in an A.C. actuated power relay.

It will be understood that many changes may be made I in details ofsolenoid construction, choice of switching arrangement, and arrangementof parts without departing from the spirit of the invention as expressedin the appended claims. It will also be understood that the applicationshown as applied to a specific power relay application is by way ofillustration only, and that the art disclosed is also beneficiallyapplicable to many other electrical control devices having currentswitching as an important function. I therefore do not wish to belimited to the exact details of construction, or arrangement of parts asshown and described.

Referring more particularly to the drawing wherein similar referencecharacters designate corresponding parts throughout the several views;FIG. 1 depicts a side elevation of the assembled relay showing themanner in which the solenoid unit is mounted atop the commercialsnap-switch 4, being enclosed by sheet-metal cover 1, which is held inassembled condition by fastening screw 7 which passes through one of thetwo mounting holes 21 in snap-switch 4, being retained by a nut on thereverse side of the assembly, not shown. Sheet-metal coverl is of agenerally U form, inverted to enclose both front and back sides of theassembly, and passing across the top of the solenoid unit to enclose andconfine the armature. The cover 1 is characterized mainly by thecentrally located raised or domed portion 22 which confines thearmature, and which has a centrally located clearance hole through whichthe head of the armature actuating screw 3 projects upwardly, thus beingexternally accessible for adjustment, or for manual operation of therelay, as for testing. Solenoid connecting leads 10 for connection tothe external control circuit pass through the solenoid magnetic shellthrough appropriate insulating means, and may be at any desirablelocation.

FIG. 2 is a partially sectioned view of the relay similar in plan toFIG. 1, in which the upper solenoid structure is sectioned on its medianplane to disclose details of construction. Switch 4 is also partiallysectioned to show the arrangement of switch actuating plunger 5. Theentire magnetic structure is contained within magnetic outer shellconstructed of annealed lowcarbon mild steel flat strip formed into aclosed rectangular loop with the abutting ends joined at bottom centerby welding, or by a locking dovetail joint, not shown. Shell 15 has inits lower surface a centrally located hole through which magnetic coreassembly 13 and 14 is firmly attached by spin-over 16, or other suitablemeans. Shell 15 has in its upper surface a bore or hole, also centrallylocated, and so dimensioned as to retain cylindrical mild steel armature2 for free vertically slidable motion therethrough. Armature 2 is thuspositioned substantially coaxial with phase-splitting core assembly13--14, and engages the upper pole-face thereof when in the downward orattracted position.

Magnetic shell 15 has a primary function of providing a closed magneticcircuit functioning to divert the flux into two separate oppositelydisposed unbroken flux paths of relatively reduced cross-section linkingthe lower end of core assembly 13-14 with the upper peripheral area ofarmature 2, external to solenoid winding 8 which is of insulated copperwire, wound on an appropriate insulating bobbin, shown in section.Cylindrical Armature 2 has a central axially aligned threaded holetherethrough in which the threaded actuating screw 3 is engaged.Actuating screw 3 is constructed of 18-8 stainless steel, bronze, orother suitable nonmagnetic material, and has threads limited to theupper portion engaging with armature 2. The rod-like lower portion ofscrew 3 extends downwardly for the full length of inner core member 14through the axial clearance hole 12 passing therethrough.

Core member 14 has in its lower end an annular recess which tightlyaccepts axial guide bushing 11 of Nylon or other .wear resistantmaterial, which has a central bearinghole dimensioned to permit thelower end portion of screw 3 to slide axially therein. The lower end ofscrew 3 is thus guided and positioned in proper axial abuttingengagement with the switch actuating plunger 5. Actuating screw 3 thushas the plural functions of operatively connecting armature 2 withswitch plunger 5, of providing an external means of adjusting the axialmotion of plunger 5 for proper switch actuation when the solenoid isenergized, and to provide axial alignment of armature 2 to avoid cockingor binding. The head of screw 3 also provides a convenient means ofmanually actuating switch 4 for test purposes. Screw 3 may be locked inthe adjusted position by the application of thread-locking compoundwhich sets after a short period of time.

Switch 4 is provided with a substantial internal nor malizing springwhich normally biases plunger 5 in an upward direction thereby acting onscrew 3 to raise armature 2 upwardly against the domed portion 22 ofcover 1, when the solenoid is deenergized. A gap is thus created betweenthe bottom face of armature 2 and the juxtaposed upper pole face formedby core members 13 and 14. Upon passage of alternating current throughsolenoid winding 8, armature 2 is drawn downward into engagement withpole members 13 and 14 by the twophase flux generated therein, beingthereafter held in firm contact thereagainst by said flux. During thedownward travel, plunger 5 is depressed thus actuating switch 4.

The mode of operation of core members 13 and 14 in generating a split ortwo-phase flux wave is based on my earlier discovery that a core memberconstructed of hysteretic material subjected to an alternatingmagnetomotive force, will respond with a flux wave lagging in phasebehind that of the magnetizing current by an amount dependent on thedegree of hysteretic remanance which is characteristic of that material.It was further determined that if the foregoing corepiece be of propercross-section it will be subject to a further phase retardation due tothe phase retardant effects of eddy or circulating currents flowingtherein. The total phase lag angle thus attained is a composite lagwhich is the vector sum of the two lag angles obtained separately by theeffects of eddy-currents and hysteresis. Very substantial phase lagangles have been found to be thus attainable. The foregoing corepiece isused in company with a companion corepiece constructed of a materialhaving a lesser hysteresis characteristic, and configured to be lesssusceptible to eddy-currents.

The two corepieces are arranged in a parallel manner, and separated by asmall gap or spacing to avoid inter-phase shunting or bypassing effects.When the two members are magnetized by the alternating current flowingin the common exciting coil, the resulting flux wave is split, with theleading phase flowing in the less retardant member, and the laggingphase flowing in the more retardant member.

Referring to FIG. 3, the outer sleeve member 13 is the leading phasemember, being constructed of annealed magnetic iron, a low hysteresismaterial. It is also provided with a longitudinal slot 17 whichinterrupts the circumferential circulating or eddy current which wouldotherwise flow therein. The inner core portion 14 is the retardant orlagging-phase member, being constructed of a moderately hystereticmaterial such as partially annealed A.I.S.I. mechanical steels C- 1115,or C-1 1 17 which are low cost and readily available steelscharacterized by a substantial value of hysteresis. Inner core 14 isconstructed as an unbroken cylindrical part, thus being subject to theflow of circular induced eddy-currents throughout its length, addingfurther to the phase retardation obtained.

The above mentioned interphase gap or separation is obtained by forminginner member 14 with a small annular step or shoulder 18 whereby thediameter of member 14 is made slightly smaller than the inside diameterof sleeve 13. A gap thickness dimension of 2% percent of the outsidediameter of sleeve 13 has been found to yield effective phaseseparation, and a highly efficient solenoid.

From the foregoing it will be apparent that I have provided novel,simple, and efficient means of attaining the objects and advantagesrecited.

Having described my invention, I claim:

1. In a magnetic relay the combination including switch means, adjacentsolenoid means having an armature, a core, a coil, and a unitary ferrousstructure exterior of said coil forming with said armature and said corea magnetic circuit, said core being of substantially cylindrical form,said external ferrous structure comprising a strip of ferrous materialforming a closed loop of substantially quadrate form having thestripends abuttingly disposed intermediate one side of said loop, theaxis of said core substantially corresponding with said abutment, andbeing substantially perpendicular thereto, said core being disposedinwardly of said external ferrous structure.

2. In a magnetic relay the combination including switch means, adjacentsolenoid means having a coil, an axially disposed core substantiallywithin said coil, an armature disposed as a plunger for axial operativemotion, and a unitary ferrous structure exterior of said coil formingwith said core and said armature a substantially closed loop magneticcircuit linking said coil, said exterior structure forming a pluralityof magnetically continuous divisional flux paths therethrough disposedabout said coil in substantial symmetry and being characterized bysubstantially co-equal magnetic crosssection.

3. A magnetic relay as set forth in claim 2 wherein said core includes acomposite flux conducting element comprising a plurality offerro-magnetic portions delin ing spaced magnetically parallel fluxpaths, said portions being relatively disparate in the electro-magneticproperties thereof including magnetic hysteresis and eddy-currentsusceptibility, said portions being magnetically separated over asubstantial portion of their common length by non-magnetic gap meansextending therebetween.

4. A magnetic relay as set forth in claim 2 wherein said switch means isof the enclosed bi-stable snapacting type having outwardly spring-biasedplunger actuating means extending outwardly thereof, and means includingscrew means joining said armature with said switch plunger actuatingmeans in threadedly adjustable operative association.

5. A magnetic relay as set forth in claim 2 wherein said armature is ofsubstantially cylindrical form arranged for axial operative motionsubstantially within said coil and said exterior ferrous structure,means including screw means joining said armature with said switch meansin threadedly adjustable operative association, a portion of said screwmeans extending outwardly of said ferrous structure whereby saidoperative association may be adjusted externally of said solenoid means.

6. A magnetic relay as set forth in claim 2 wherein said armature andsaid,core are of substantially cylindrical form disposed in an axiallyco-extensive manner, said armature being arranged for axial operativemotion, cover means enclosing at least one side of said solenoid means,said core defining the energized limit of motion of said armature, aportion of said cover means providing stop means defining thede-energized limit of motion of said armature.

1. In a magnetic relay the combination including switch means, adjacentsolenoid means having an armature, a core, a coil, and a unitary ferrousstructure exterior of said coil forming with said armature and said corea magnetic circuit, said core being of substantially cylindrical form,said external ferrous structure comprising a strip of ferrous materialforming a closed loop of substantially quadrate form having thestrip-ends abuttingly disposed intermediate one side of said loop, theaxis of said core substantially corresponding with said abutment, andbeing substantially perpendicular thereto, said core being disposedinwardly of said external ferrous structure.
 2. In a magnetic relay thecombination including switch means, adjacent solenoid means having acoil, an axially disposed core substantially within said coil, anarmature disposed as a plunger for axial operative motion, and a unitaryferrous structure exterior of said coil forming with said core and saidarmature a substantially closed loop magnetic circuit linking said coil,said exterior structure forming a plurality of magnetically continuousdivisional flux paths therethrough disposed about said coil insubstantial symmetry and being characterized by substantially co-equalmagnetic cross-section.
 3. A magnetic relay as set forth in claim 2wherein said core includes a composite flux conducting elementcomprising a plurality of ferro-magnetic portions defining spacedmagnetically parallel flux paths, said portions being relativelydisparate in the electro-magnetic properties thereof including magnetichysteresis and eddy-current susceptibility, said portions beingmagnetically separated over a substantial portion of their common lengthby non-magnetic gap means extending therebetween.
 4. A magnetic relay assEt forth in claim 2 wherein said switch means is of the enclosedbi-stable snap-acting type having outwardly spring-biased plungeractuating means extending outwardly thereof, and means including screwmeans joining said armature with said switch plunger actuating means inthreadedly adjustable operative association.
 5. A magnetic relay as setforth in claim 2 wherein said armature is of substantially cylindricalform arranged for axial operative motion substantially within said coiland said exterior ferrous structure, means including screw means joiningsaid armature with said switch means in threadedly adjustable operativeassociation, a portion of said screw means extending outwardly of saidferrous structure whereby said operative association may be adjustedexternally of said solenoid means.
 6. A magnetic relay as set forth inclaim 2 wherein said armature and said core are of substantiallycylindrical form disposed in an axially co-extensive manner, saidarmature being arranged for axial operative motion, cover meansenclosing at least one side of said solenoid means, said core definingthe energized limit of motion of said armature, a portion of said covermeans providing stop means defining the de-energized limit of motion ofsaid armature.